Oxidative dehydrogenation of cyclic hydrocarbons



of peroxides.

Patented Dec. 1, 1953 OXIDATIVE DEHYDROGENATION OF CYCLIG HYDROCARBONSBernard Orkin, Philadelphia, Pa., assignor to Socony-Vacuum Oil Company,Incorporated, a corporation of New York No Drawing. Application February20, 1951, Serial No. 211,975

16 Claims. 1

The present invention relates to the dehydrogenation of cyclichydrocarbons and, more particularly, to the oxidative dehydrogenation ofcyclic hydrocarbons to produce a substantially non-oxygenated product.

Moureu, Dufraisse and Chaux, in Compt. rend. vol. 184, 413 (1927)disclosed that decalin autoxidizes at room temperature with theformation Kroger and Struber in Naturwiss, vol. 32, 229 (1944) havedescribed the oxidation of decalin with elementary oxygen at 120-150 C.to yield such products as oxides of carbon, hydrogen, water, formicacid, naphthalene, phthalic acid and, as a preponderant product, aresinous material. Shimose, in Sci. Papers Inst. Phys. Chem. Research(Tokyo) vol. 15, 251 (1931) has shown that when decalin vapor and airare passed over ammonium vanadate-molybdate catalyst at 490-510 C.phthalic anhydride is obtained. Chowdhury, in J. Ind. Chem. Soc. vol.14, 638 (1937) has disclosed that vapor phase oxidation of decalin witha large excess of air over tin vanadate on asbestos yields phthalicanhydride, maleic anhydride, succinic anhydride, formaldehyde and oxidesof carbon. It has also been shown by Nametkin and Rozenberg in Chem.Abs. vol. 39, 3902 (1945) that decalin has been oxidized to naphthaleneand a number of other substances at 575 C.

According to Hartmann and Seiberth, Helv. Chim. Acta, vol. 15, 1390(1932), tetralin has been oxidized to the'hydroperoxide while Hook and.Susemihl, Berichte, vol. 66, 61 (1933) report that tetralin has beenoxidized to tetralone and Chernozhukov reports in J. Applied Chem.(USSR) vol. 8, 251 (1935) that tetralin is oxidized to acids andphenols. Maxted has reported in Trans. J. Soc. Chem. Ind. vol. 47, 101(1928) that tetralin with oxygen in the vapor phase at 280 C. over a tinvanaclate catalyst gives a 50 per cent yield of phthalic anhydride.Green has reported that a 67 per cent yield of phthalic anhydride can beobtained by the oxidation of tetralin over vanadium oxide, on pumice at340 C. and with vanadium oxide on silica gel at 400-475 C.

2 Shreve and Welborn report that a better than per cent yield ofphthalic anhydride has been obtained. (Ind. Eng. Chem. vol. 35, 279(1943)).

The formation of trace amounts of benzene and naphthalene has beenreported by Nametkin and Rozenberg (ibid. supra).

Senderens, Ann. Chim. (9) 13, 283; Wagner U. S. Patent 2,386,372; Berl,Heise and Winnacker, Z. Physik. Chem. (A) 139, 457; Chowdhury andSaboor, J. Ind. Chem. Soc. 14, 638

(1937); Rust, Haley and Vaughn, U. S. Patent 2,421,392; Milas and Walsh,J. Am. Chem. Soc. 61, 633 (1939); Shmidl, U. S. Patent 2,474,334; andHamvlet and McAlevy, U. S. Patent No. 2,439,513; report the oxidation ofcyclohexane with air to maleic acid. It is to be noted that Milas andWalsh also report that a small quantity of benzene is obtained inaddition to the maleic acid. The catalysts employed are respectively,silver, silver oxide, iron carbonyl, tin vanadate, hydrogen bromide,vanadium oxide on pumice, vanadium oxide on silica gel, and cobaltnaphthenate.

Methylcyclohexane has been oxidized to the corresponding ketone bypassing a mixture of the cycloparafiin with air over a silver oxidecatalyst at 400-500 C. (Wagner, U. S. Patent 2,386,372).

Cyclohexane has been oxidized to maleic acid over vanadium oxide [Milasand Walsh, J. Am. Chem. Soc. 61, 633 (1939)]. The use of iron andperoxide catalysts in the oxidation of cyclohexane has been suggested byBerl, Heise and Winnacker (ibid. supra), and in British Patent 534,- 525respectively.

Partial oxidation of hydrocarbon oils such as keroseneor gasoline hasbeen accomplished in elongated tubes in the absence of catalyst asdisclosed in U. S. Patents Nos. 1,767,291 and 1,898,168. In the VoorheesU. S. Patent No. 2,351,793 the oxidation of oil in the presence offinely divided siliceous catalysts at temperatures above 750 F. isdescribed; the catalyst being present to the extent of about 25 per centto about 600 per cent by weight of the hydrocarbon o1 Oxidation ofdecalin and tetralin to naphthalene in low yield in a mixture ofoxygenated hydrocarbons has been reported to take place in the absenceof a catalyst at 575 C.

Vasilev and Glushner, Chem. Abs. 43, 81242 (1949) are said to haveexperimented with oxidative reforming but obtain only low yields.

Thus, it is apparent that prior art attempts to oxidativelydehydrogenate decalin, tetralin, cyclohexane and in general cyclichydrocarbons has resulted in low yields of the corresponding lesssaturated hydrocarbon in admixture with a predominating yield ofoxygenated products.

It has now been discovered that decalin, tetralin, cyclohexane, methylcyclohexane and in general cyclic hydrocarbons having a nuclear hydrogen-..to-ca=rbon-1ratio greater than -1:-1 can be oxidatively.dehydrogenated to the corre-; sponding less saturated hydrocarbon, i.e., having a nuclear hydrogen carbon ratio not greater than 1:1employing silica gel, or telluriumoxide on a support as a catalyst.

When substantially pure hydrocarbons 'serve as the feed material in thepresentzanethod, i.. -.e.,.v

decalin, tetralin, cyclohexana. methylcyclohex? ane, oxidativedehydrogenation takes place to.

yield a substantially non-oxygenated product.

However, when a mixture of cyclic hydrocarbonsand non-cyclichydrocarbons such as a petroleum naphtha is the feed material similarreactions take place but, because of the initial presence of-1 compoundsother .than cycloparaflins, oxygen; containing compounds also areformed.

Oxidative dehydrogenationof' decalin, tetralin,cyclohexane;methylcyclohexane was obtained by passing amixture of thehydrocarbon-mixed with 100 per cent to 400 per cent excessof that-theo-' reticallyrequiredof oxygenbr .air or in general free-oxygencontaining-gas overthe catalyst at temperatures of :about 5503-950'Fpwith a pre-. fer-red; temperature of about. '740'760 F.- Thereactorwas :keptimmersed in'a constant .tem pera-ture salt bath and thehydrocarbon and-oxygen 'orzair wereintroduced in. metered amountsthrough. separate preheater coils at .the bottom of.-.the, reactor.Efiluent: was collectedin :aisuit.-. able trap. and analyzed. Althoughall of the runs. reported herein were carriedloutrat, atmos. pheric,subatmospheric.pressures can be used.

Thecatalyst can be silica gel purse or inacona junctionlwith a'tellurium oxide catalyst. A. tel.- lurium-oxide catalyst, can, also besupported by an inert-support such as tabular alumina: asbestos or thelike.

The :runs reported herein; were conducted. in the spacevelocity-rangeof: abut.0.1'to about 0.6." The lower space velocity rates are moresuitable -for the oxidative:dehydrogenation of substantiallypurehydrocarbons where the oxygen concentration is high. When the oxygenconcen:-. tra-tionyis low'and/ or littlegheat. is,ydevelop.ed, a space.velocity ofabout 3.0 .issatisfactory. Thus, liquid hourly spacevelocities (LHSV) of about.0.1.. to about 3.5 to 4 are suitable.

Liquid hourly space. velocity is..-defined as. the ratio ofthevolumeofliquid charge passed perhour over aunit volume of catalyst, for example,c:c. liquid charge/c. c. catalyst/hr.

Itisof interest to note that in;copending application for United StatesLetters Patent Serial No. 139,529, filed-January l9, 1950,.the oxidationofactivatedmethyl or methylene groups to carbonyl groups employing acatalyst comprisingatleast one-oxide of tellurium; is. disclosed. Con,-

sequently, it is surprising to discover that a catalyst comprising atellurium oxide is useful for oxidatively dehydrogenating cyclichydrocarbons without the formation of substantial amounts of oxygenatedproducts.

The oxidative dehydrogenation of cyclic hydrocarbons such as decalin,tetralin, cyclohexane, methyl cyclohexane to naphthalene, cyclohexeneand benzene, and methyl cyclohexene respectively, is achieved by passingpreheated hydrocarbon and oxidizing gas containing free oxygen through areactor in contact with a catalyst, or a catalyst on an inert support ashereinafter indicated, and separating the dehydrogenated hydrocarbonfrom unreacted hydrocarbon and other products of the reaction. With suchexceptions as, are noted hereinaftertherreactor.iwassa glass reactor Inthe indicatedinstances theglass reactor was replaced by a metal reactorfabricated 'fofz-xstainless steel #347 said to contain nickel:

8-.12. percent;.chromium:l'7-20 per cent; carbon=0 :l0.::per cent max;columbium=1.0 per cent max; iron=67-'75 per cent.

It. is tube .noted that when tetralin vapor and oxygen :are'passed'vovertellurium oxide on alumina oron: silica -gel, i. e., an inactive and anactive supportrespectively, the hydrocarbon was dehydrogenated tonaphthalene. The reaction is essentially an oxidation since onlynegligible con- -'ver-si0ns=i.=e., 1 per cent to 3 per cent, wereobtained in the absence of oxygen.

Silica: gel: was foundwto-rbera catalyst for fthe oxidativedehydrogenation. of. the substantially pure hydrocarbons; aswwellvas:for commercial. naphthas: Commercial naphthas whensubjeetedi tooxidative dehydrogenation using silicagel alone showed i definiteimprovement. in: octane number as well as :an'increase in: bromine numther.

The data obtained in' a series of runs is =tabulated in the followingtable's-which are believed to be self-explanatory forthose'skilledin-the art.

TABLE I Efie'ct of metallic tellurium and alumina "on thedehydrogenation of tetralm to naphmalene'iw the absence of oxygenPercentco1Iversion-mol pcrcentzconversion of tetralin' tonaphtha lens in1 pass...

Catalyst-(6.3 gutellurium oxide 'IeOz'on cc: alumina) was reduced; with.hydrogen.-

Tellurium metal (6-10 mesh) was oxidized with oxygen and re-.

duced-with hydrogen (several cycles).

It will be notedthat-inthe absence of oxygen the conversion of tetralin'to naphthalene was:

negligible.-

TABLE II Efiect of inert support on dehydrogenation of tetralz'n tonaphthalene in the presence or oxy- MR-mols oxygen per mol of tetralin.

b Percent conversion-mol percent conversion of tetralin to naphthalenein 1 pass.

9 Metal reactor used in this run. a Air substituted for oxygen.

It will be observed that substitution of air for oxygen reduces theconversion in one pass when using silica gel as the catalyst from 82 percent to 34 per cent. It Will also be noted that such relatively inertsupports as quartz and tabular alumina produce some conversion.

TABLE III Efiect of telllnrzum dioxide on alumina catalyst ondehydrogenation of tetralin to naphthalene in the presence of oxygenTemperature, F. Sg Run Oxygen, Tetralin, MR 8 Time, com Cata- No.moles/hr. moles/hr. hours veb lyst Bath g' sion MR-mols oxygen per molof tetralin.

17 Percent conversion-mol percent conversion of tetralin to naphthalenein 1 pass.

9 Air substituted for oxygen.

' Metal reactor used in this run.

9 6.3 g. tellurium oxide per 100 cc. alumina. f 1.5 g. tellurium oxideper 100 cc. alumina.

B 10.0 g. tellurium oxide per 100 cc. alumina.

It will be observed that .5 grams of tellurium oxide per 100 cc. ofsupport has little or no catalytic effect. On the other hand, 6.3 gramstellurium oxide per 100 cc. of support increased the conversion by about58 per cent. According1y,it is preferred to have at least about 2 grams01 tellurium oxide per 100 cc. of support.

TABLE IV Effect of tellurium dioxide on silica gel catalyst ondehydrogenation of tetralinto naphthalene in the presence of owl/genemperature, F. 5. Run Oxygen Tetralin, MR0 Time, com Cata- No. Rmoles/hr. moles/hr. hours lyst Bath actor sion l 9.3 g. tellurium oxideper 100 cc. (mufiied) silica gel. b 7.0 g. tellurium oxide per 100 cc.silica gel. 9 MRmols oxygen per mol of tetralin.

Percent conversionmo1 percent conversion of tetralin to naphthalene in 1pass.

B Air substituted for oxygen. 1 Metal reactor used in this run.

Comparison of the conversions achieved in Runs Nos. 22 and 23 indicatesthe efiect of reactor temperature upon the yield and establishes thatpreferred reactor temperatures are of the order of 740-760 F.

TABLE V Dehydroyenation of decalin to naphthalene in the presence ofoxygen Temperature, F. 5g;

Run Oxygen, Decalin Time Cata- No. R moles/hr. moles/hr. MR c hours lystBath sion 1 25. 720 735 d 0. 099 0 030(0) 3. 3 2. 0 1 26. 715 715 042035(0) 1. 2 2. 0 1 27. 745 765 092 024(0) 3. 8 1. 4 17 28. 645 670 093024(0) 3. 9 1. 2 9 29. 570 590 097 025(0) 3. 9 1. 5 3 30.-. 745 770 094030(T) 3. 1 1. 5 18 31. 635 670 095 030(T) 3. 2 1. 4 6 32 760 787 093024(0) 3. 9 2. O 22 versions are achieved at about 760-790 F.

TABLE VI Dehydrogenation of cyclohemane to cyclohezene in the presenceof oxygen Tempera- P R o O Cycloc0211;

un xygen, Time Cata- No. moles/hr. MR hours lyst mo es/hr. ver- Bathactor sion 11 n 6.3 g. tellurim oxide per cc. alumina.

b 10.0 g. tellurium oxide per 100 cc. alumina.

v 7. g. tellurium oxide per 100 cc. silica gel.

d In addition, 4 percent conversion to benzene.

= In addition, 3 percent conversion to benzene.

I MRmoles of oxygen per mole of cyclohcxane.

is Air substituted for oxygen.

11 Percent conversionmo1c percent conversion of cyclohexane tocyclohexene in 1 pass.

I Metal reactor used in this experiment.

1 Silica gel.

egocnsso:

TABLE VII Dehydrogenatzon of methylcycloheacame tom eth ylcyclohexene inthe presence 0;orryge1r Tempera- Methylcyclo R ture, F. O hexane T 5;;

un xygen, une, No. moles/hr. M hours fig; Catalyst Bath 3; cm. Moles/hr.510m.-

43-.. 435 485 0. 105 6. 3 O. 064 1. 6 2. 7 O 44.-.. 645 045 067 7. 6 07787 2.15 7 (Q 45.-. 760 760 031 5. 5 056 54 2. 1 16 (a 46.... 700 690 1718. 8 090 1.9 2.3 i 14 47..- 700 690 092 9. 4 096 1. 6 '7 18 (E 700 690044 9. 4 096 46 1. 3 13 49-" 750 785 l 104 7. 1 072 1.4 1. 3* d 3 1- 50650 685 1 104 6. 4 065 1. 6 1. 5 c 4 6.3 gJTeO; per 100 cc. alumina; b10.0:g.'Teoaiperi100ccla1umina.: 7.0 g..TeO.-; per 100cc. silica gel. dIn addition,8% conversion totoluerre. e In addition;-4%conversiontotoluene'. In addition, 4% conversion to toluene. K Inaddition, 2% conversion to toluene. MR1:uoles of oxygen per mole ofmethylcyclohexane. i Air substituted for oxygen.

Peroent conversion-mole percent conversion of methylcyclohcxane to moth;I

cyclohexenc:

k Metal reactor used in thisexperiment.

1 Silica gel.

TABLE VIII Dehydrogenation of cyclohexene to benzene in the presence ofoxygen un xygen; rule, can No. moles/hr. hrs. conver- Catalyst BathReacton- GJhr. Moles/hr.

54..- 760' 810 1 010 1" I 0.098 1.1 1.3 22 Silica gel. 55... 635 670.104 .093 1.1 1.5 9 Do. 56... 503' I 515 .1024" .102 1.0 1.1 1 Do. f

e MR moles of oxygen perrmole' of yelohexene. b Airrsubstitutedfor-oxyge1 1.--v

* Percent conversion-mole percent conversion of cyclohexene to benzene.f It is of interestto note that when'oXygem-is From the data presentedin. TableVIII it is manifest that for the oxidative dehydrogenation ofcyolohexene to benzene theipreferredtemperature is in excess of 810F-.',' say from about 810 F to about/850 replaced' "by nitrogen :thereis no dehydrogenation as.- measured. by the. increase. in brominenumber. treated state had a bromine-.numb'enof 3.8"when TABLE IXDehydrogematwvt of naphthas m the presence of oxygen i Weight: pResearch. Run Charge Temp, Charge Oxygen, OM31 st oercent API' Bromineoctane No. stock" F. LSV d cc./hr. v y recovgravity: N 0. number. ery. Iclean.

. 65.1 0.6 61 57... 740- 0. 71 1, 830 '63.'3 18.3 6817 58... 745 0.77 1,260 63. 9 10.?5 65.0 46.8 3.8 55 59... 750 0.63 1, 770 44. 9 18. 7 69.060..- 730 0.59 1, 950 44. 4 16. 1 61 (8)" 755 0.48 1, 920 41. 4 21.573.0 62... 805 0.50 1,970. 45. 3 '18. 7 68.0 63... 865 0. 44 1,970 47.0:19. 2 67. 0 64..- 765 0.59 1, 950 44. 8 15. 1 65.0 65..- 855 0. 40 1,950 45. 4 12. 6 64. 0 06... 750 0. 48 9,180N. 45.8 1. 2 54. 5 67..- 7500.48 9,'180A,v 45. 3 8.0 60.0 68..- 750 0. 48 9, 000A 69..- 750 0. 48 9,000A 43.1 17. 4 67. 0 55.1 0. 9 T 441A 855 0. 46 1, 980 54.6 '9. 8 53. 5745 0.64 1, 980 53. 7 15. 3 56. 5 750 0. 63 '1, 950 53.6 13. 2 56.0 8450. '66 1, 920 53. 7 '10. 0' 54:0 750 0.63 1,980 750 0. 55 l, 920 62. 31G. 7 6010 755 0.62 1, 950 50. 7 24. 4 68. 0 750 0. 63 9, 000N 55. 1 0.645. 0

Oklahoma City light naphtha boiling range 151 F.-244 F. b GeneralPetroleum straight run heavy naphtha boiling range 0 Agha Iari fullboiling range naphtha boiling range 181 'F.-388

*Naphthas containing .cyclo'paraflins particularly cyclohexane andmethylcycloh'eirane.'v

d LSVliquid space velocity-volumeof liquid naphtha perumt volume ofcatalyst per hour; v Nnitrogen substituted for oxygen. A-airsubstituted[or oxygen. 1 Recovery of total liquid product from water-cooled and DryIce-cooled traps.

1 (Describe stock 741 as above.) In (Describe "stock 742 as above.)

Thus, a naphtha which in- ,the' un 9 passed in admixture with nitrogenover silica gel actually had a lower bromine number after treatment thanbefore. (See Table IX, Runs No. 66.)

I claim:

1. A method of oxidative dehydrogenation of canbocyclic hydrocarbonswhich comprises mixing a first carbocyclic hydrocarbon in which thenumber of hydrogen atoms directly attached to nuclear carbon atoms isgreater than the number of unsubstituted nuclear carbon atoms with a gascontaining free oxygen, the amount of oxygen in the resultant mixturebeing at least about 100% in excess of the theoretical amount requiredto produce by oxidation 2. second carbooyclic hydrocarbon having fewerhydrogen atoms directly attached to nuclear carbon atoms than said firstcarbocyclic hydrocarbon, contacting said mixture with a catalystselected from the group consisting of silica gel, tellurium oxide,

carbon atoms is less than said first carbocyclic hydrocarbon.

2. A method of oxidative dehydrogenation of tetralin which comprisesmixing tetralin with a gas containing free oxygen in amount sufiicientto provide 100% to 400% oxygen in excess of that theoretically requiredto dehydrogenate said tetralin to naphthalene by oxidation, contactingthe resultant mixture with a catalyst selected from the group consistingof silica gel, tellurium oxide, and silica gel and chromia attemperatures of about 600 F. to about 775 F. and separating naphthalene.

3. The method of oxidative dehydrogenating tetralin to naphthalene asdescribed and set forth in claim 2 wherein the catalyst is tel uriumoxide.

4. A method of oxidative dehydrogenation of decalin which comprisesmixing decalinv with a gas containing free oxygen in amount sufficientto provide 100% to 400% oxygen in excess of that theoretically requiredto dehydrogenate said decalin' to naphthalene by oxidation, contactingthe resultant mixture with a catalyst selected from the group silicagel, tellurium oxide, and silica gel and chromia at temperatures ofabout 590 F. to about 790 F., and separating naphthalene.

5. The method of oxidative dehydrogenating decalin to naphthalene as setforth and described in claim 4 wherein the catalyst is tellurium oxideon silica gel.

6. A method of .oxidative dehydrogenation of cyclohexane which comprisesmixing cyclohexane with a gas containing free oxygen in amountsuiilcient to provide 100% to 400% oxygen in excess of thattheoretically required to dehydrogenate cyclohexane to cyclohexene byoxidation, contacting the resultant mixture with a catalyst selectedfrom the group consisting of silica gel, tellurium oxide, and silica geland chromia at a temperature of about 700 to about 750 F., andseparating cyclohexene.

7. The method of oxidative dehydrogenating cyclohexane to cyclohexene asdescribed and set forth in claim 6 wherein the catalyst is telluriumoxide.

8. A method of oxidative dehydrogenation of methylcyclohexane whichcomprises mixing methylcyclohexane with a gas containin free oxy en inamount sufficient to provide 100% to 400% oxygen in excess of thattheoretically required to dehydrogenate methylcyclohexane tomethylcyclchexene by oxidation, contacting the resultant mixture With acatalyst selected from .the group consisting of silica gel, telluriumoxide, and silica gel and chromia at a temperature of about 635 to about760 F., and separating methylcyclohexene.

9. The method of oxidative dehydrogenating methylcyclohexane tomethylcyclchexene as described and set forth in claim 8 wherein thecatalyst is tellurium oxide.

10. A method of oxidative dehydrogenation of cycloparaifins to thecorresponding aromatic hydrocarbon of the benzene series which comprisesmixing a cycloparaffin having a single six membered ring and not morethan one methyl substituent with a gas containing free oxygen in amountsufiicient to provide to 400% oxyen in excess of that theoretic-allyrequired to dehydrogenate said cycloparafiin to a cycloolefin byoxidation, containing the resulting mixture with tellurium oxide at atemperature of about 635 to about 760 F., and separating an aromatichydrocarbon oi the benzene series.

11. A method of oxidative dehydrogenation of cyclohexene to benzenewhich comprises mixing cyclohexene with a gas containing free oxygen inamount sufficient to provide 100% to 400% oxygen in excess of thatrequired to dehydrogenate said cyclohexene to benzene by oxidation,contacting the resulting mixture with tellurium oxide at a temperatureof about 515 to about 810 F., and separating benzene.

12. A method of raising the octane number of a petroleum naphtha whichcomprises mixing a petroleum naphtha with a gas containing free oxygenin amount sufficient to provide 100% to 400% oxygen in excess of thattheoretically required, contacting the resultant mixture with a silicagel catalyst at a temperature of about 550 to about 950 F., andseparating a naphtha having an improved octane number and an increasedbromine number.

13. A method of raising the octane number of a petroleum naphtha whichcomprises mixing a petroleum naphtha with gas containing free oxygen inamount sufficient to provide 100% to 400% oxygen in eXcess of thattheoretically required, contacting the resultant mixture with asilicachromia catalyst at temperatures of about 730 F. to about 865 F.,and separating a naphtha having an improved octane number and increasedbromine number.

14. The method set forth and described in claim 13 wherein the liquidspace velocity is less than 1.

15. A method of oxidative dehydrogenation of carbocyclic hydrocarbonswhich comprises mixing a first carbocyclic hydrocarbon in which thenumber of hydrogen atoms directly attached to nuclear carbon atoms isgreater than the number of unsubstituted nuclear carbon atoms with a gascontaining free oxygen, the amount of oxygen in the resultant mixturebeing about 100% to about 400% in excess of that theoretically requiredto produce by oxidation from the first carbocyclic hydrocarbon a secondcarbocyclic hydrocarbon having fewer hydrogen atoms attached to nuclearcarbon atoms than said first carbocyclio hydrocarbon, contacting saidmixture with a catalyst selected from the group consisting oi silicagel, tellurium oxide and silica gel and chromia at a temperature ofabout 550 to about 950 F. and separating a carbocyclic hydrocarbon whichthe umber-b h dro en a om directly attachedto nuclear carbon atoms isless than said first carbocyclic hydrocarbon.

16. A method of oxidative dehydrogenation of carbocyclic hydrocarbonswhich comprises mixin a first carbocyclic hydrocarbon in which thenumber of hydrogen atoms directly attachedsiio nuclear carbon atoms isgreater thanthe number of unsaturated nuclear carbon atoms with a gascontainingfree oxygen, the amount of oxygenin the resultant mixturebeinginexcessof the theoretical amount required toproduce by oxidationa-second carbocyclic hydrocarbonhav- .ing fewer hydrogen atoms directlyattached to nuclearcarbon atoms than said first carbocyclic hydrocarcon,contacting said mixture with, tel-, luriumioxide in themesence of anickel-chroma.- ironc alloy. containing. 842%, nickel, 17-20% chromium,67-75% iron, 1.0% (maximum) molybdenumand 010% (maximum) ca1 bon,--at atemperature of about- 55.0-to about 950 R, and

12 separating a carbocyclic.hydrocarbonin which the number of hydrogenatoms d rectlyattached to. nuclear carbon atoms is ,less than saidjrstcarbocyclic hydrocarbon,

BERNARD ORKIN.

References Ci1:.ed.rin .thefile, of lthis patent UNITED,STATES PATENTSNumber Name Date.

1,214,204 Mann et a1. Jan; 30, 1917 1,984,519 Chappell Dec.18,'19342,077,994 Ellis Apr. 20,' 19 37 2,143,380 Klein et al. .Jan. 10," 19392,347,805 Bell May 2; 1944 2,350,834 Sensel 'et a1. June 6,19442,351,793 Voorhees' et al. June 20; 1944 2,378,209 Fuller et a1. June21, 1945 OTHER REFERENCES Nametkin et a1., Chem. Abstracts, Vol.39, page3902 (1945).

1. A METHOD OF OXIDATIVE DEHYDROGENATION OF CARBOXYCLIC HYDROCARBONSWHICH COMPRISES MIXING A FIRST CARBOCYCLIC HYDROCARBON IN WHICH THENUMBER OF HYDROGEN ATOMS DIRECTLY ATTACHED TO NUCLEAR CARBON ATOMS ISGREATER THAN THE NUMBER OF UNSUBSTITUTED NUCLEAR CARBON ATOMS WITH A GASCONTAINING FREE OXYGEN, THE AMOUNT OF OXYGEN IN THE RESULTANT MIXTUREBEING AT LEAST ABOUT 100% IN EXCESS OF THE THEORETICAL AMOUNT REQUIREDTO PRODUCE BY OXIDATION A SECOND CARBOCYCLIC HYDROCARBON HAVING FEWERHYDROGEN ATOMS DIRECTLY ATTACHED TO NUCLEAR CARBON ATOMS THAN SAID FIRSTCARBOCYCLIC HYDROCARBON, CONTACTING SAID MIXTURE WITH A CATALYSTSELECTED FROM THE GROUP CONSISTING OF SILICA GEL, TELLURIUM OXIDE, ANDSILICA GEL AND CHROMIA, AT A TEMPERATURE OF ABOUT 550* TO ABOUT 950* F.,AND SEPARATING A CARBOCYCLIC HYDROCARBON IN WHICH THE NUMBER OF HYDROGENATOMS DIRECTLY ATTACHED TO NUCLEAR CARBON ATOMS IS LESS THAN SAID FIRSTCARBOCYCLIC HYDROCARBON.